The standard procedure for making a multipart workpiece, for instance a wheel hub, is to first fit a base or first workpiece with a second workpiece. For instance a cylindrical base workpiece can be fitted with a ring. To this end the base workpiece is mounted in a holder and the ring is fitted to a jig. The holder presses the base workpiece up against the ring to fit them together, then the fitted-together parts are shifted to a welding station where they are rotated under a welding head that joins them along a circular seam.
Such an apparatus is described in DE 199 47 588 A1. Specified as different laser machining processes are material removal, material deposition, hardening and welding. The holding device can be moved under digital control in at least two axis running transverse to one another and, by means of a pressing process, can bring two workpieces into a defined position relative to one another for laser welding. The holding device is configured as a workpiece spindle rotatable about an axis. Further, a laser beam head is provided which can be pivoted about two axes. For joining a flange shaft and a bell-shaped workpiece, a chuck adapted to the workpiece geometry and an annular holddown or jig are provided in the holding means.
While this system works well, whenever workpiece size changes, it is necessary to shut down the entire machine and change the holddowns and jigs. This can represent a significant loss of production.